How Inflatable Seat Belts Work

The biggest news this past week from the automotive industry, in terms of safety innovations at least, was Ford's announcement it has completed work on the world's first inflatable seat belts – a brilliant combination between the seat belt and the attributes of an airbag. We know, just by looking at the name of the innovation, you can't but wonder why did we have to develop them only now, in 2009, given the fact that seat belts have been around since the mid-1850s (or 1885, if we count from Edward J. Claghorn's patent for a device "designed to be applied to the person, and provided with hooks and other attachments for securing the person to a fixed object"), while airbags came to be in the late 1960s. Unfortunately, we don't have an answer to this dilemma. Inflatable seat belts are one of those ideas, so simple it makes you wonder "why in the world didn't I come up with it first?" As Srini Sundararajan, Ford safety technical leader said: "It’s a very simple and logical system, but it required extensive trial and error and testing over several years to prove out the technology and ensure precise reliable performance in a crash situation.” HISTORY
Ford has been working on the inflatable seat belts for some time now, with the first reference to them made in 2006, when the American carmaker also said it is working on a four-point seat belt system, together with TRW Automotive. Back then, Stephen Rouhana, Ford safety research and advanced-engineering group senior technical leader estimated the seat belts will be ready for use by the end of the decade (2010).


The inflatable seat belts are, as the name suggests, seat belts with the ability to inflate when needed. They look like the regular ones, except for the fact that they are a bit wider and feel softer, thanks to the accordion-folded airbags hidden inside. The belt is connected to vehicle sensors, used to detect a collision and give the belts the signal to inflate.


When the aforementioned sensors detect a collision is occurring, the signal is sent to the belt's airbags to inflate. Unlike regular airbags, which inflate thanks to a heat-generating chemical reaction, the seat belts use cold compressed gas to do so.

The choice to use gas instead of chemicals was made because, unlike in the case of regular airbags, these ones are literally on the passenger's body. This means that using heat to inflate the bag was not a viable choice, given the high risk for the passenger. The gas used for the task, Ford says, feels no warmer than the ambient temperature.

Once the gas has been released through a buckle from a cylinder housed below the seat, each of the tubular, accordion -folded airbags inflate and expand to cover over the wearer's torso and shoulder, providing better protection for a larger area of the body, as well as a tighter hold thanks the increased size.

The speed at which the airbags fill with air is slower than in a regular one, given the fact that it is already pressed against the wearer's body through the seat belt and does not need to prevent him from hitting anything. The whole process, from detection to inflation, lasts only 40 milliseconds.

Once the hazard has passed and the belt has done its job, the air in the airbag is released through the pores of the bag itself.


According to the initial data obtained by Ford, once inflated, the airbag covers five times more of the occupant’s torso than the usual seat belt. This means more injuries are avoided thanks to the fact that the force used to hold the occupant in place is distributed to a larger area. This in turn also means the occupant has better support for the head and neck.

The inflatable seat belts will prove to be more reliable and safe when it comes to protecting children. All those who have been in a crash know that regular seat belts have a tendency to leave their mark on the one whose life they save. In children's case, the higher the speed of collision, the higher the risk of injuries. This is not the case with the inflatable seat belts.


Ford and its partners have put quite a lot of work and money into the project, so the first vehicles to get the new inflatable seat belts will be the 2011 Ford Explorer. After that, the sky is the limit. Of course, there will be those arguing that the belts or the airbags inside would have to be replaced after each deployment...

We reckon the new seat belts will soon turn standard on more Ford models and perhaps will be adopted by the whole industry.

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About the author: Daniel Patrascu
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Daniel loves writing (or so he claims), and he uses this skill to offer readers a "behind the scenes" look at the automotive industry. He also enjoys talking about space exploration and robots, because in his view the only way forward for humanity is away from this planet, in metal bodies.
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